Mid Year exams Flashcards
State the names of the four phases of mitosis
Prophase, metaphase, anaphase, telophase
Draw typical eukaryotic cells as they would appear during the interphase and the four phases of mitosis.
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Outline four events that occur during prophase
- DNA condenses into chromosomes and become visible
- Centrioles move to opposite poles
- The nuclear membrane starts to dissolve
- Chromosomes are comprised of genetically identical sister chromatids
Outline the process of metaphase, inclusive of the role of microtubules and the kinetochore.
- all the chromosomes line up in the middle of the cell
- spindle microtubules attach to the chromosomes at its centromere
- the attachment site is called the kinetochore
Outline the process of anaphase
- uses ATP
- sister chromatids are pulled to opposite poles
- chromatids are now considered an individual chromosome
Outline four events that occur during telophase
- chromosomes begin to uncoil
- spindle fibres disappear
- nuclear membrane reforms
- cytokinesis occurs
Describe the structure of a replicated chromosome, include the centromere and sister chromatids.
- centrioles organise spindle microtubules
- centromere is the part of a chromosome that links sister chromatids
- spindle microtubules pull chromosomes to opposite poles
- sister chromatids are duplicated chromosomes attached by a centromere
- in animal cells, two centrioles are help by a protein mass referred to as a centrosome
- after the sister chromatids separate they should then be referred to as chromosomes
Explain why chromosomes must be condensed during mitosis
Chromosomes need to be condensed to be able to fit within the nuclei of the cells
Describe the formation of the cleavage furrow in animal cell cytokinesis
- a ring of contractile protein at the equator pulls the plasma membrane inward
- the inward pull on the plasma membrane produces the characteristic cleavage furrow
- when the cleavage furrow reaches the centre of the cells it is pinched apart to form two daughter cells
Describe the formation of the middle lamella and cell wall in plant cytokinesis
- during telophase, membrane-enclosed vesicles derived from Golgi apparatus line up along the equator of the parent cell
- the vesicles fuse together to form the cell plate
- vesicles deposit, by exocytosis, pectins and other substances in the lumen between the daughter cells to form the middle lamella (gluing the cells together) of the new cell wall
- each of the two daughter cells then secrete cellulose between their new cell membrane and the middle lamella, to form the primary cell wall
State the formula for calculation of a mitotic index
Cells in mitosis divided by the total number of cells
State the location of the light independent reactions of photosynthesis
Occurs in the stroma
State that the light independent reactions of photosynthesis include:
- Carbon fixation
- carboxylation of RuBP
- Production of trios-phosphate
- ATP and NADPH as energy sources
- ATP is used to regenerate RuBP
- ATP is used to produce carbohydrates
The process of light independent reactions
- Carbon fixation: carbon dioxide enters plants and goes into stroma. The carbon dioxide attaches to ribulose bisphosphate in a process called carbon fixation (RuBP is carboxylated with carbon dioxide, catalyzed by rubisco). An unstable 6C is formed and immediately splits into 2 glycerate 3-phosphate.
- The G3P molecules are reduced by ATP and NADPH to form 2 triose phosphate molecules
- Regeneration: RuBP reforms at the expense of ATP. Most of the TP molecules produced are used to regenerate RuBP. Some of the TP are linked to form glucose phosphate
- (not a step) ATP and NADPH produced in light dependent are used in light independent
Define carbon fixation
The incorporation of inorganic carbon into organic compounds
Define carboxylation
The combination of carbon dioxide with an organic compound
State that carbon fixation occurs in the chloroplast stroma
State that carbon fixation occurs in the chloroplast stroma
State that the 5-carbon molecule ribulose bisphosphate (RuBP) is carboxylated by CO2, forming 2 3-carbon molecules called Phosphoglycerate (PGA).
• State that the 5-carbon molecule ribulose bisphosphate (RuBP) is carboxylated by CO2, forming 2 3-carbon molecules called Phosphoglycerate (PGA).
State that the enzyme that catalyzes the carboxylation of RuBP is called ribulose bisphosphate carboxylase (rubisco).
• State that the enzyme that catalyzes the carboxylation of RuBP is called ribulose bisphosphate carboxylase (rubisco).
Define variation
Individuals vary from one another in many characteristics. Variation is inherited
Explain why natural selection can only function if there is variation in a species
- Some characteristics in variation are more favorable than others.
- Individuals with well-adapted variations will survive and reproduce
- These characteristics will increase
Outline how a “selective pressure” acts on the variation in a population.
Competition for resources, change in environment, or predators allows individuals with varying characteristics to compete and pass on favorable traits to next generation
List examples of “selective pressures.”
Change in environment, predators, competition
Explain the effect of the selective pressure on the more and less adapted individuals in a population.
More adapted individuals will survive and reproduce offspring with the favorable characteristics. Less well-adapted species will be eliminated due to their poor characteristics
Define biomass.
The total mass of a group of organisms
Define keystone species (giving examples).
A keystone species (exert a top-down influence on lower trophic levels) is one which has a disproportionate effect on the structure of an ecological community (Sea otters regulate sea urchin populations, starfish)
Outline the impact of removing a keystone species on food chain/web.
Removing a keystone species will cause lower trophic levels to monopolize critical resources, such as competition for space or food sources
Explain what a climograph shows.
A climograph is a diagram which shows the relative combination of temperature and precipitation in an area.
Outline the difference between open and closed ecosystems.
In a closed ecosystem energy but not matter is exchanged with the surroundings.
Define biomass.
The dry weight of an organism
Outline nutrient inputs and outputs shown on a Gersmehl diagram (including) and how they flow between sinks.
Nutrient inputs into the ecosystem:
• Nutrients dissolved in raindrops
• Nutrients from weathered rock
Nutrient outputs (losses) from the ecosystem:
• Nutrients lost through surface runoff
• Nutrients lost through leaching
Nutrients are stored in one of three nutrient sinks – either as biomass, litter or soil
Nutrients can be transferred between nutrient sinks and may also be cycled via environmental inputs and outputs
Nutrients can be transferred from biomass to litter (fallout), litter to soil (decay) or soil to biomass (uptake)
Litter can additionally gain nutrients via precipitation (rainfall) and lose nutrients in surface runoff
Soil can gain nutrients from the erosion of rocks via weathering, but will lose nutrients via leaching
Define alien species
An alien species is one which arrives in a non-native habitat, usually as the intentional or accidental result of human activity
Give examples of plant and animal alien species, and explain the impact on native species
The cane toad was introduced to Australia other parts of the world to control agricultural crop pests. It is now classed as an invasive species as it has reproduced so heavily, and it’s toxic skin is a threat to other animals and predators.
Define competitive exclusion
-Two species cannot occupy the same niche in a community as there will bee competition for the same resources
-When one species has even the slightest advantage or edge over another then the one with the advantage, will dominate
Define biomagnification
A process in which chemical substances become more concentrated at each trophic level
define bioaccumulation
When individual eats contaminated food or filters, contaminated water and builds up chemical substances within them
What is the effect of DDT on Falcons?
Reproductive issues and shell thinning
What are the benefits of using DDT?
- Affordable and effective at killing mosquitoes that carry malaria
- alternative strategies were not a successful
- Health costs greatly reduced
- Where DDT was discontinued, rates and deaths of malaria increased
What are the limitations of using DDT?
- People exposed to DDT, may suffer serious health affects
- DDT lasts in the environment for a long time
Define biotic index
A biotic index compares the relative frequency of indicator species
discuss the area effect on species richness
- The larger the area the more species it can support
- Larger areas offer a greater diversity of habitats
- More niches
- Increase in breeding
Define top down limiting factors
Factors are pressures applied by other organisms at higher trophic levels
Define bottom up limiting factors
Factors are those that involve resources or lower trophic levels
What are ecological impacts when fisheries collapse?
- interdependence of species
- Loss of diversity and productivity
- r-strategists and Pests could proliferate
What are economical and social impacts when fisheries collapse
- long-term recession of the industry
- Unemployment
- loss of food source
- Damage to communities and culture
Discuss maximum sustainable yield
MSY is the largest catch possible without adversely affecting the ability of the population to recover.
Up to the maximum sustainable yield, sufficient individuals are replaced in the stock year-on-year so that there is no overall population decline.
Outline methods, used to estimate the size of commercial fish stocks
Fish catch data:
- volume of catch
- catch rate
- catch rate by age of fish
Lincoln Index:
- useful in lakes
- difficult with small fish
- unreliable in open ocean (migration makes reliability poor)
Technology:
- echolocation can generate an estimate of school size
- satellite images can track migration of schools or large individuals
Outline the bottom up control of algal blooms by shortage of nutrients
- nutrients are essential for the synthesis of key proteins and other compounds
- Algae, depends on photosynthesis for nutrition
- With key proteins in short supply, the rate of photosynthesis, and hence algal growth is limited
Outline the top-down control of algal blooms by herbivory
- parrotfish are herbivores that graze on free-living algae at lower trophic levels. This is an example of top-down control of algae.
What is the impact of water logging on the nitrogen cycle?
- Waterlogging, reduces the oxygen availability in soils
- Waterlogging encourages the process of denitrification by bacteria
- leads to greater leaching of nutrients, which leads to nutrient enrichment of rivers and lakes and therefore to eutrophication
